Sensitivity (ISO/ASA/DIN)

The ISO (International Standards Organization) number is the value of sensitivity.A low ISO setting or value of a film needs more light to be effective, while a high ISO needs less light.High ISO numbers are better for darker shots, while lower ISO numbers are better for daylight.This number determines the light-capturing capability of a film or a sensor. For digitals this can be varied. For film cameras once a film is installed, you'll need to set the correct ISO setting on the camera to get proper pictures.The ISO number is the last of the 3 settings that determine the EV (exposure value) of your scene/camera setup. These are again: the shutter speed, the aperture value and the ISO.This triangle is bound together. If you change one up, you'll need to change another one down in order to maintain the pre-set EV.E.g.: if you open the aperture 1 stop (8->5.6) you'll need to shorten the shutter speed e.g.: from 125 to 250.If you have a digital camera and wish to preserve your shutter speed, you can go for changing the ISO setting e.g.: from 200 to 100.What is ASA, ISO and DIN?These are all the same but expressed differently. Here is a small conversion table: ASA - DIN - ISO------------------------------- 50 - 18 - 50/18° 100 - 21 - 100/21° 200 - 24 - 200/24° 400 - 27 - 400/27° 800 - 30 - 800/30° 1600 - 33 - 1600/33°

Same image with same exposure, however the ISO value is different. Graininess and noise appears.